Cooling is one issue of devices used in the space environment. For example, although a cooling device installed in a space suit is required to cool coolant, ambient air or environmental water (seawater and the like) is not available as a cooling source, differently from cooling devices used on the ground. This implies that a cooling technique different from that used on the ground is required for achieving cooling in the space environment.
One known cooling device for use in the space environment is a sublimator, which uses the latent heat of evaporation of water to cool an object. A sublimator is disclosed in Rubik B. Sheth et al., “Investigation of Transient Performance for a Sublimator”, 41st International Conference on Environmental Systems, 17-21 Jul. 2011, Portland, Oreg., United States (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100021978_2010023392.pdf).
FIG. 1 is a cross-sectional view showing the structure of the sublimator disclosed in this document, which is denoted by numeral 100. Feedwater layers 102 and 104 are coupled to both surfaces of a coolant layer 103, respectively, and sublimation plates 101 and 105 are coupled to the feedwater layers 102 and 104, respectively. The coolant layer 103 is used as a path which coolant to be cooled passes through, and the feedwater layers 102 and 104 are used as paths which feedwater passes through. The sublimation plates 101 and 105 are made of porous stainless steel sheet. The feedwater supplied to the feedwater layers 102 and 104 are introduced into the sublimation plates 101 and 105, respectively, and then evaporated into the space environment. This allows capturing heat from the coolant in the coolant layer 103, thereby cooling the coolant.
Other cooling devices which use latent heat of evaporation of water for cooling in the space environment are disclosed, for example, in Japanese Patent Publication No. 2782272 B. The cooling device disclosed in this publication also achieves cooling of the coolant by evaporating water through porous material.
One issue of these cooling devices for use in the space environment is that the porous plate is easily clogged, if the purity of the water used for cooling is low. This undesirably causes deterioration in the cooling efficiency. These cooling devices require high-purity water as the feedwater to be evaporated or sublimated.